Disease-associated autoantibodies during pregnancy and at birth in families affected by type 1 diabetes.

We studied the pattern of type 1 diabetes-associated autoantibodies during pregnancy and the transplacental transfer of these autoantibodies to the fetal circulation and searched for possible signs of prenatal induction of beta-cell autoimmunity in newborn infants. The population comprised 208 mothers and their newborn infants. Seventy-four of the mothers (36%) had type 1 diabetes and 134 (64%) of the infants had an affected father or sibling. Blood samples were obtained from the mother at the end of the first trimester and at delivery, and from the cord blood of the newborn infant. Close to 40% of the mothers with type 1 diabetes had antibodies to islet cells (ICA), 55% to glutamic acid decarboxylase (GADA) and 54% to the IA-2 protein (IA-2A) in early pregnancy, whereas the corresponding frequencies in the nonaffected mothers were 5.2%, 5.2% and 3.0%. No significant changes could be seen in autoantibody levels during pregnancy, and there was a close correlation between the two maternal samples. One third of the infants of mothers with type 1 diabetes tested positive for ICA, 50% for GADA and 51% for IA-2A. Six percent of the infants of nondiabetic mothers had ICA, 2.2% GADA and none had IA-2A. None of the infants of the antibody negative mothers had antibodies in their cord blood. These observations indicate that the immunomodulatory effect of pregnancy on signs of beta-cell autoimmunity is weak, but if diabetes-associated autoantibodies are present in the mother, most of them are transferred to the fetal circulation. Our data do not provide any support for fetal induction of beta-cell autoimmunity.

Disease-associated antibodies in offspring of mothers with IDDM.

We studied 20 infants of mothers with IDDM participating in a pilot study for a dietary intervention trial, testing the hypothesis that avoidance of cow's milk proteins early in life will reduce the risk of subsequent IDDM. The aim was to evaluate the elimination of IDDM-associated antibodies from the peripheral circulation of the infants, the possible emergence of autoantibodies indicating beta-cell destruction, and the influence of the dietary intervention and genetic disease susceptibility on the development of these autoantibodies. Transplacentally transferred islet cell antibodies (ICAs) and antibodies to the 65-kDa isoform of glutamic acid decarboxylase (GAD65As) disappeared from the peripheral circulation of most infants over the first few months of life and in all infants before the age of 9 months. Insulin antibodies were eliminated before the same age in all cases but one. The higher the initial antibody level was, the longer the time required for elimination. Four infants tested positive for insulin autoantibodies (IAAs) on at least one occasion during the first year of life, and 5 out of 16 unaffected subjects (31%) had IAAs at the age of 2 years. One infant became positive for IAA before the age of 6 months, with increasing levels later, seroconverted to positivity for ICAs and GAD65As between 6 and 9 months and presented with clinical IDDM at the age of 14 months. He had the HLA DQB1*0302/x genotype, which predisposes carriers to IDDM, and had been given the casein hydrolysate formula as supplementary milk. There were no significant differences in the levels of various autoantibodies between two groups of subjects defined either on the type of dietary intervention or the degree of genetic susceptibility. The findings indicate that transplacentally transferred antibodies related to IDDM are usually eliminated from the peripheral circulation of infants before 9 months of age and that IDDM-associated autoantibodies may emerge before the age of 6 months. Our results also illustrate that avoidance of cow's milk proteins over the first 9 months of life does not provide total protection against IDDM.